Vector network analyzer with digital interface

ABSTRACT

A measuring device includes a first measuring port connected to an optical interface which can be connected to an optical input or output of a device under test (DUT). The device includes a second measuring port which can be connected to a radio frequency (RF) input or output of the DUT. The optical interface is connected to the optical input of the DUT and the second measuring port is connected to the RF output of the DUT. The first measuring port generates an analog measuring signal and provides it to the optical interface. The optical interface generates an optical measuring signal based on the analog measuring signal and provides it to the optical input of the DUT. The second measuring port receives an analog measuring signal generated by the DUT based on the optical measuring signal. The processor determines S-parameters of the DUT based on the two analog measuring signals.

RELATED APPLICATIONS

This application is a continuation and claims the benefit of the earlierfiling date under 35 U.S.C. § 120 from U.S. application Ser. No.17/205,740 (filed 2021 Mar. 18), which is a continuation and claims thebenefit of the earlier filing date under 35 U.S.C. § 120 from U.S.application Ser. No. 15/898,874 (filed 2018 Feb. 19), now U.S. patentSer. No. 11/041,894 (issued 2021 Jun. 22), which claims the benefit ofthe earlier filing date under 35 U.S.C. § 119(e) from U.S. ProvisionalApplication Ser. No. 62/547,195 (filed 2017 Aug. 18), the entireties ofwhich are incorporated by reference herein.

TECHNICAL FIELD

The invention relates to a network vector analyzer, and a measuringmethod using a measuring device (such as vector network analyzer), whichallow the measurement of scattering parameters (in the followingS-parameters) of devices under test. The measuring device may also havean optical input or output.

BACKGROUND

A regular vector network analyzer has at least two analog measuringports. A device under test is supplied with an analog input signal andreacts by generating an analog output signal. The input signal isprovided by a measuring port of the network analyzer, while the analogoutput signal is measured by a further measuring port of the vectornetwork analyzer. By comparing the input signal and the output signal,the S-parameters of the device under test are determined.

In recent years, more and more devices under test with only a singleanalog port, be it an input or an output, have come into existence. Forexample, a remote radio head of a base-station comprises an opticalinput and an analog radio frequency output. It is therefore not possibleto determine the S-parameters of such a device with a conventionalvector network analyzer.

For example, the U.S. Pat. No. 8,508,237B2 shows a conventional vectornetwork analyzer having only analog radio frequency ports. There, acalibration device is shown, which encompasses an interface fromelectrical signals to optical signals and also an optical calibrationstandard.

Accordingly, there is a need for a vector network analyzer that canperform S-parameter measurements on devices under test having digital oroptical ports.

Some Example Embodiments

Embodiments of the present invention advantageously address theforegoing requirements and needs, as well as others, by providing ameasuring device (such as a vector network analyzer), and a measuringmethod using a measuring device (such as a vector network analyzer),which can perform S-parameter measurements on devices under test havingdigital or optical ports.

According to a first aspect of the invention, a measuring device (suchas a vector network analyzer) is provided. The vector network analyzercomprises a first measuring port, a first digital interface, connectedto the first measuring port, adapted to be connected to a digital inputor output of a device under test, a second measuring port adapted to beconnected to a radio frequency input or output of the device under test,a processor adapted to determine S-parameters of the device under testbased on measuring signals transmitted to the device under test andreceived from the device under test, by the first measuring port and thesecond measuring port. It is thereby possible to determine theS-parameters of the device under test while using only a single radiofrequency port of the device under test.

According to a first implementation form of the first aspect, whereinthe first digital interface is connected to a digital input of thedevice under test, and the second measuring port is connected to a radiofrequency output of the device under test, the first measuring port isadapted to generate a first analog measuring signal and supply it to thefirst digital interface, the first digital interface is adapted togenerate a first digital measuring signal from the first analogmeasuring signal, the first digital interface is adapted to provide thefirst digital measuring signal to the digital input of the device undertest, the second measuring port is adapted to receive a second analogmeasuring signal from the device under test, which the device under testgenerates based on the first digital measuring signal, and the processoris adapted to determine the S-parameters of the device under test fromthe first analog measuring signal and the second analog measuringsignal. It is thereby possible to accurately determine S-parameters forthe case of a digital input of the device under test.

According to a second implementation form of the first aspect, whereinthe first digital interface is connected to a digital output of thedevice under test and the second measuring port is connected to a radiofrequency input of the device under test, the second measuring port isadapted to generate a third analog measuring signal and supply to theradio frequency input of the device under test, the first digitalinterface is adapted to receive a second digital measuring signal, whichthe device under test generates based on the third analog measuringsignal, the first digital interface is adapted to generate a fourthanalog measuring signal based on the second digital measuring signal,and the processor is adapted to determine the S-parameters of the deviceunder test from the third analog measuring signal and the fourth analogmeasuring signal. Also for the case of a digital output of the deviceunder test, it is possible to accurately determine the S-parameters.

According to a third implementation form of the first aspect, themeasuring device further comprises a first measuring port connectoradapted to connect the radio frequency input or output of the deviceunder test to the first measuring port, a first digital interfaceconnector adapted to connect the digital input or output of a deviceunder test to the first digital interface, and a coupler adapted toconnect the measuring port to first measuring port connector and to thefirst digital interface connector. It is thereby possible to selectivelyhave a connection between the first measuring port and the digitalinterface or the connector.

According to a fourth implementation form of the first aspect, themeasuring device further comprises a third measuring port and a firstoptical interface connected to the third measuring port adapted to beconnected to an optical input or output of a device under test. Theprocessor is then adapted to determine the S-parameters of the deviceunder test based on measuring results transmitted to the device undertest and received from the device under test by the first measuring portand/or the second measuring port and/or the third measuring port. It isthereby possible to additionally handle optical signals, whichsignificantly increase the flexibility of the measuring device.

According to a fifth implementation form of the first aspect, whereinthe first optical interface is connected to an optical input of thedevice under test and the second measuring port is connected to a radiofrequency output of the device under test, the third measuring port isadapted to generate a fifth analog measuring signal and supply it to thefirst optical interface, the first optical interface is adapted togenerated a first optical measuring signal from the fifth analogmeasuring signal, the first optical interface is adapted to provide thefirst optical measuring signal to the optical input of the device undertest, the second measuring port is adapted to receive a sixth analogmeasuring signal from the device under test, which the device under testgenerates based on the first optical measuring signal, and the processoris adapted to determine the S-parameters of the device under test fromthe fifth analog measuring signal and the sixth analog measuring signal.This approach allows for receiving optical signals by the device undertest and the determining S-parameters therefrom. This increases theflexibility of the measuring device.

According to a sixth implementation form of the first aspect, whereinthe first optical interface is connected to an optical output of thedevice under test and the second measuring port is connected to a radiofrequency input of the device under test, the second measuring port isadapted to generate a seventh analog measuring signal and supply it tothe radio frequency input of the device under test, the first opticalinterface is adapted to receive a second optical measuring signal, whichthe device under test generates based on the seventh analog measuringsignal, the first optical interface is adapted to generate an eighthanalog measuring signal based on the second optical measuring signal,and the processor is adapted to determine the S-parameters of the deviceunder test from the seventh analog measuring signal and the eighthanalog measuring signal. It is thereby possible to also handle receivingoptical signals from the device under test. This furthermore increasesthe flexibility of the measuring device.

According to a seventh implementation form of the first aspect, themeasuring device further comprises a second measuring port connectoradapted to connect the radio frequency input or output of the deviceunder test to the third measuring port, a first optical interfaceconnector adapted to connect the digital input or output of the deviceunder test to the first optical interface, and a further coupler adaptedto connect the third measuring port to the second measuring portconnector and to the first optical interface connector. It is therebypossible to selectively have a connection between the third measuringport and the optical interface or the respective measuring portconnector directly.

According to an eighth implementation form of the first aspect, thevector network analyzer additionally comprises a fourth measuring portadapted to be connected to a further radio frequency input or output ofthe device under test, a fifth measuring port, and a second digitalinterface, connected to the fifth measuring port, adapted to beconnected to a further digital input or output of the device under test.The processor is then adapted to determine S-parameters of the deviceunder test based on measuring signal transmitted to the device undertest and received from the device under test by the first measuringport, the second measuring port, and the fourth measuring port. Byhaving two digital interfaces, two digital signals transmitted by orreceived from the device under test can be handled while determining theS-parameters. This significantly increases the flexibility of themeasuring device.

According to a ninth implementation form of the first aspect, whereinthe first digital interface is connected to a digital Inphase-parameter(in the following I-parameter) input of the device under test, thesecond digital interface is connected to a digital quadrature phaseparameter (in the following Q-parameter) input of the device under test,the fourth measuring port is connected to a local oscillator input ofthe device under test, and the second measuring port is connected to aradio frequency output of the device under test, the first measuringport is adapted to generate a first analog I-parameter signal andprovide it to the first digital interface, the first digital interfaceis adapted to generate a first digital I-parameter signal and provide itto the digital I-parameter input of the device under test, the fifthmeasuring port is adapted to generate a first analog Q-parameter signaland provide it to the second digital interface, the second digitalinterface is adapted to generate a first digital Q-parameter signal andprovide it to the digital Q-parameter input of the device under test,the fourth measuring port is adapted to generate a local oscillatorsignal and provide it to the local oscillator input of the device undertest, the second measuring port is adapted to receive a ninth analogmeasuring signal and the processor is adapted to determine theS-parameters of the device under test from the first analog I-parametersignal, the first analog Q-parameter signal, the local oscillator signaland the ninth analog measuring signal. It is thereby possible to measureon devices having a digital I/Q-interface as an input.

In a tenth implementation form of the first aspect, wherein the firstdigital interface is connected to a digital I-parameter output of thedevice under test, the second digital interface is connected to adigital Q-parameter output of the device under test, the fourthmeasuring port is connected to a local oscillator input of the deviceunder test, and the second measuring port is connected to a radiofrequency input of the device under test, the fourth measuring port isadapted to generate a local oscillator signal and provide it to thelocal oscillator input of the device under test, the second measuringport is adapted to generate a tenth analog measuring signal and provideit to the radio frequency input of the device under test, the firstdigital interface is adapted to receive a second digital I-parametersignal and generate a second analog I-parameter signal therefrom, thesecond digital interface is adapted to receive a second digitalQ-parameter signal and generate a second analog Q-parameter signaltherefrom, the first measuring port is adapted to receive the secondanalog I-parameter signal, the fifth measuring port is adapted toreceive the second analog Q-parameter signal, and the processor isadapted to determine the S-parameters of the device under test from thesecond analog I-parameter signal, the second Q-parameter signal, thelocal oscillators signal and the tenth analog measuring signal. Therebyit is possible to process devices under test having a digital I/Q-outputinterface. This significantly increases the flexibility of the measuringdevice.

According to a second aspect of the invention, a method for measuringthe scattering parameters of a device under test is provided. The methodcomprises connecting a device under test to a digital interface of avector network analyzer, connecting the device under test to a measuringport of the vector network analyzer, supplying a digital measuringsignal, generated from a first analog measuring signal, to the deviceunder test via the digital interface, measuring a second analogmeasuring signal, generated by the device under test as a reaction tothe digital measuring signal, via the measuring port of the vectornetwork analyzer, and determining scattering parameters of the deviceunder test from the first analog measuring signal and the second analogmeasuring signal. This allows for determining the scattering parametersof a device under test having a digital input port.

According to a third aspect of the invention, a method for measuring thescattering parameters of a device under test is provided. The methodcomprises connecting a device under test to a digital interface of avector network analyzer, connecting the device under test to a secondmeasuring port of the vector network analyzer, supplying a first analogmeasuring signal to the device under test via the second measuring port,receiving a digital measuring signal via the first digital interface andgenerating a second analog measuring signal therefrom, measuring thesecond analog measuring signal via the first measuring port, anddetermining S-parameters of the device under test from the second analogmeasuring signal and the first analog measuring signal. This allows fordetermining the scattering parameters of a device under test having adigital output. This significantly increases the flexibility of themeasuring method.

According to a fourth aspect of the invention, a method for measuringthe scattering parameters of a device under test is provided. The methodcomprises connecting a device under test to a first digital interface ofa vector network analyzer, connecting the device under test to a seconddigital interface of the vector network analyzer, connecting the deviceunder test to a first measuring port of the vector network analyzer,connecting the device under test to a second measuring port of thevector network analyzer, generating a first analog Inphase-parametersignal via a third measuring port, providing a digital I-parametersignal, generated from the analog I-parameter signal, to the deviceunder test via the first digital interface, generating an analogquadrature phase parameter signal via a fourth measuring port, providinga digital Q-parameter signal, generated from the analog Q-parametersignal, to the device under test via the second digital interface,providing a local oscillator signal to the device under test via thefourth measuring port, measuring an analog measuring signal via thesecond measuring port, and determining scattering parameters of thedevice under test from the analog measuring signal, the local oscillatorsignal, and the analog I-parameter signal and the first analogQ-parameter signal. This allows for measuring the S-parameters of adevice under test having a digital I/Q-parameter input. Thissignificantly increases the flexibility of use of the method.

According to a fifth aspect of the invention, a method for measuring thescattering parameters of a device under test is provided. The methodcomprises connecting a device under test to a first digital interface ofa vector network analyzer, connecting the device under test to a seconddigital interface of the vector network analyzer, connecting the deviceunder test to a first measuring port of the vector network analyzer,connecting the device under test to a second measuring port of thenetwork vector analyzer, providing a local oscillator signal to thedevice under test via the second measuring port, providing an analogmeasuring signal to the device under test via the first measuring port,receiving a digital Inphase (I)-parameter signal and determining ananalog I-parameter signal therefrom, receiving a digital quadraturephase (Q)-parameter signal and determining an analog Q-parameter signaltherefrom, and determining the scattering parameters of the device undertest from the second analog I-parameter signal, the analog Q-parametersignal, the local oscillator signal, and the analog measuring signal.This allows for performing measurements on a device under test having adigital I/Q-parameter output. This significantly increases theflexibility of the method.

Still other aspects, features, and advantages of the present inventionare readily apparent from the following detailed description, simply byillustrating a number of particular embodiments and implementations,including the best mode contemplated for carrying out the presentinvention. The present invention is also capable of other and differentembodiments, and its several details can be modified in various obviousrespects, all without departing from the spirit and scope of the presentinvention. Accordingly, the drawing and description are to be regardedas illustrative in nature, and not as restrictive.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention are illustrated by way of example,and not by way of limitation, in the figures of the accompanyingdrawings, in which like reference numerals refer to similar elements,and in which:

FIG. 1 shows a vector network analyzer according to the prior art;

FIG. 2 shows a first embodiment of a vector network analyzer adapted toperform S-parameter measurements on device(s) under test, in accordancewith example embodiments of the present invention;

FIG. 3 shows a second embodiment of a vector network analyzer adapted toperform S-parameter measurements on device(s) under test, in accordancewith example embodiments of the present invention;

FIG. 4 shows a third embodiment of a vector network analyzer adapted toperform S-parameter measurements on device(s) under test, in accordancewith example embodiments of the present invention;

FIG. 5 shows a fourth embodiment of a vector network analyzer adapted toperform S-parameter measurements on device(s) under test, in accordancewith example embodiments of the present invention;

FIG. 6 shows a fifth embodiment of a vector network analyzer adapted toperform S-parameter measurements on device(s) under test, in accordancewith example embodiments of the present invention;

FIG. 7 shows a sixth embodiment of a vector network analyzer adapted toperform S-parameter measurements on device(s) under test, in accordancewith example embodiments of the present invention;

FIG. 8 shows a first embodiment of a method for measuring the scatteringparameters of device(s) under test, in accordance with exampleembodiments of the present invention;

FIG. 9 shows a second embodiment of a method for measuring thescattering parameters of device(s) under test, in accordance withexample embodiments of the present invention; and

FIG. 10 shows a third embodiment of a method for measuring thescattering parameters of device(s) under test, in accordance withexample embodiments of the present invention.

DETAILED DESCRIPTION

Approaches for a measuring device (such as a vector network analyzer),and measuring methods using a measuring device (such as a vector networkanalyzer), which can perform S-parameter measurements on devices undertest having digital or optical ports, are described. It is apparent,however, that the invention may be practiced without these specificdetails or with an equivalent arrangement. In other instances,well-known structures and devices are shown in block diagram form inorder to avoid unnecessarily obscuring the invention.

As will be appreciated, a module or component (as referred to herein)may be composed of software component(s), which are stored in a memoryor other computer-readable storage medium, and executed by one or moreprocessors or CPUs of the respective devices. As will also beappreciated, however, a module may alternatively be composed of hardwarecomponent(s) or firmware component(s), or a combination of hardware,firmware and/or software components. Further, with respect to thevarious example embodiments described herein, while certain of thefunctions are described as being performed by certain components ormodules (or combinations thereof), such descriptions are provided asexamples and are thus not intended to be limiting. Accordingly, any suchfunctions may be envisioned as being performed by other components ormodules (or combinations thereof), without departing from the spirit andgeneral scope of the present invention. Moreover, the methods, processesand approaches described herein may be processor-implemented usingprocessing circuitry that may comprise one or more microprocessors,application specific integrated circuits (ASICs), field programmablegate arrays (FPGAs), or other devices operable to be configured orprogrammed to implement the systems and/or methods described herein. Forimplementation on such devices that are operable to execute softwareinstructions, the flow diagrams and methods described herein may beimplemented in processor instructions stored in a computer-readablemedium, such as executable software stored in a computer memory store.

Further, terminology referring to computer-readable media or computermedia or the like as used herein refers to any medium that participatesin providing instructions to the processor of a computer or processormodule or component for execution. Such a medium may take many forms,including but not limited to non-transitory non-volatile media andvolatile media. Non-volatile media include, for example, optical diskmedia, magnetic disk media or electrical disk media (e.g., solid statedisk or SDD). Volatile media include dynamic memory, such random accessmemory or RAM. Common forms of computer-readable media include, forexample, floppy or flexible disk, hard disk, magnetic tape, any othermagnetic medium, CD ROM, CDRW, DVD, any other optical medium, randomaccess memory (RAM), programmable read only memory (PROM), erasablePROM, flash EPROM, any other memory chip or cartridge, or any othermedium from which a computer can read data.

First, the problems of a prior art vector network analyzer are addressedwith reference to FIG. 1 . Then, with reference to FIG. 2 -FIG. 7 ,different embodiments of a vector network analyzer, which can performS-parameter measurements on device(s) under test having digital oroptical ports, in accordance with example embodiments of the presentinvention, are described in detail with regard to their construction andfunction. Finally, with reference to FIG. 8 -FIG. 10 , differentembodiments of measuring methods for measuring the scattering parametersof a device under test, in accordance with example embodiments of thepresent invention, are described. Similar entities and reference numbersin different figures have been partially omitted.

Reference will now be made in detail to example embodiments of thepresent invention, examples of which are illustrated in the accompanyingdrawings. However, the following embodiments of the present inventionmay be variously modified and the range of the present invention is notlimited by the following embodiments. Further, in the followingdescription, the term measuring port is used in the sense of an entiremeasuring path, including the entire signal processing with regard to asingle signal (not only the connector of the vector network analyzer ismeant).

FIG. 1 shows a regular vector network analyzer 1 according to the priorart. The network vector analyzer 1 comprises a first measuring port 11,a second measuring port 12 and a processor 16, connected to the firstmeasuring port 11 and the second measuring port 12.

A device under test 2 is connected to the first measuring port 11 andthe second measuring port 12. The first measuring port 11 provides aradio frequency signal to the device under test 2, which generates aradio frequency output signal as a response. The signal is measured bythe second measuring port 12. From the signal generated by the firstmeasuring port 11 and the signal received by the second measuring port12, the processor 16 determines the scattering parameters (S-parameters)of the device under test 2.

FIG. 2 shows a first embodiment of a vector network analyzer 3 adaptedto perform S-parameter measurements on device(s) under test, inaccordance with example embodiments of the present invention. The vectornetwork analyzer 3 here comprises a first measuring port 31 and a secondmeasuring port 32. The first measuring port 31 is additionally connectedto a digital interface 311, which in turn is connected to a digitalinput of the device under test 2. The device under test 2 is connectedto the second measuring port 32 with its radio frequency output. Whenperforming a measurement, the first measuring port 31 generates a firstanalog measuring signal 380 and supplies it to the digital interface311. The digital interface 311 therefrom generates a first digitalmeasuring signal 381 and supplies it to the digital input of the deviceunder test 2. The device under test 2 therefrom generates a secondanalog measuring signal 382, which is measured by the second measuringport 32. From the first analog measuring signal 380 and the secondanalog measuring signal 382, the processor 36 determines theS-parameters of the device under test 2.

FIG. 3 shows a second embodiment of a vector network analyzer 4 adaptedto perform S-parameter measurements on device(s) under test, inaccordance with example embodiments of the present invention. Here, thevector network analyzer 4 comprises a first measuring port 41, a secondmeasuring port 42 and a third measuring port 43. The first measuringport 41 is connected to a coupler 413, which in turn is connected to afirst measuring port connector 412. The coupler 413 is moreoverconnected to a first digital interface 411, which again is connected toa first digital interface connector 410. The third measuring port 43 isconnected to a coupler 433, which is connected to a second measuringport connector 432 and to a second optical interface 431, which in turnis connected to an optical interface 431, which in turn is connected toa first optical interface connector 430. The coupler 413 couples thedigital interface 411 and the connector 412 to the first measuring port41. The coupler 433 connects the optical interface 431 and the connector432 to the third measuring port 43.

In the example shown here, the second measuring port 42 generates ananalog measuring signal 480 and provides it to a radio frequency inputof the device under test 2. The device under test 2 generates an opticalmeasuring signal 481 therefrom and provides it to the optical interface431 through the optical connector 430. The optical interface 431converts the signal to an analog measuring signal 482, which is providedby the coupler 433 to the third measuring port 43. The analog measuringsignal 482 is measured by the third measuring port 43. The processor 46determines the S-parameters of the device under test 2 from the analogmeasuring signals 480 and the analog measuring signal 482.

FIG. 4 shows a third embodiment of a vector network analyzer 5 adaptedto perform S-parameter measurements on device(s) under test, inaccordance with example embodiments of the present invention. In FIG. 4, the vector network analyzer 5 comprises a first measuring port 51, asecond port 52, a fourth measuring port 54 and a fifth measuring port55. The first measuring port 51 is connected to a coupler 513, which isconnected to a measuring port connector 512 and to a digital interface511, which in turn is connected to a digital interface connector 510.The fifth measuring port 55 is connected to a coupler 533, which isconnected to a measuring port connector 552 and to a digital interface551, which in turn is connected to a digital interface connector 550.All measuring ports 51, 52, 54 and 55 are connected to a processor 56.

Here, for a device under test 2 having a digital Inphase (I)-input and aquadrature phase (Q)-input, a local oscillator input and a radiofrequency output is measured. The digital interface connector 510connects the interface 511 to the I-signal input of the device undertest 2. The digital interface connector 550 connects the digitalinterface 551 to the Q-signal input of the device under test 2. Themeasuring port 54 is connected to a local oscillator input of the deviceunder test 2. The measuring port 52 is connected to the radio frequencyoutput of the device under test 2.

When performing a measurement, the first measuring port 51 generates ananalog I-parameter signal S80 and provides it via the coupler 513 to thedigital interface 511. The digital interface generates a digitalI-parameter signal S84 therefrom and provides it to the device undertest 2. The measuring port 55 generates an analog Q-parameter signal S81and provides it via the coupler 553 to the digital interface 551. Thedigital interface 551 generates a digital Q-parameter signal S85therefrom and provides it to the device under test. The measuring port54 generates a local oscillator signal S82 and provides it to the deviceunder test. The second measuring port 52 measures a radio frequencyoutput signal S83 of the device under test 2. The processor 56determines the S-parameters of the device under test 2 from the analogI-parameter signal 580, the analog Q-parameter signal 581, the localoscillator signal 582 and the analog measuring signal 583 measured bythe second measuring port 52.

FIG. 5 shows a fourth embodiment of a vector network analyzer 6 adaptedto perform S-parameter measurements on device(s) under test, inaccordance with example embodiments of the present invention. In FIG. 5, the vector network analyzer 6 comprises five measuring ports 61-65,each connected to a joint processor 66. The first measuring port 61 isconnected to a coupler 613, which again is connected to a digitalinterface 611. The third measuring port 63 is connected to a coupler633, which in turn is connected to an optical interface 631. The fifthmeasuring port 65 is connected to a coupler 653, which in turn isconnected to a digital interface 651.

Here, two digital interfaces, two regular measuring ports and oneoptical interface are shown. Each of the interfaces is preferablybi-directional. Alternatively, the interfaces can be mono-directional.Also the number of measuring ports and interfaces is not to beunderstood as limiting. A number of one, two, three, four or moredigital and/or optical interfaces can be employed. Also a number of one,two, three, four, five, six, seven, eight, nine, ten or more measuringports can be used.

With regard to the embodiments of FIG. 2-5 , the number of measuringports need not be limited to the depicted number. Just as well, 6, 7, 8,9, 10, or more measuring ports can be present within the measuringdevice according to example embodiments of the present invention.Further, the number of optical interfaces and digital interfaces alsoneed not be limited to the number shown in such embodiments. By way ofexample, the number of optical and/or digital interfaces may be up tothe total number of measuring ports. In further accordance with suchexample embodiments, calibration of all the measuring ports, opticalinterfaces and/or digital interfaces is possible.

FIG. 6 shows a fifth embodiment of a vector network analyzer 7 adaptedto perform S-parameter measurements on device(s) under test, inaccordance with example embodiments of the present invention. In FIG. 6, the measuring device 7 comprises a first measuring port 70 connectedto an optical interface 71 and the second measuring port 73. Theremaining components of the measuring device 7 are not displayed in FIG.6 as they are as shown in FIGS. 2-5 .

By way of example, the device under test is a photodiode 72, which isconnected to the optical interface 71 on its optical side and to thesecond measuring port 73 on its electrical side. Since the firstmeasuring port 70 in conjunction with the optical interface 71, as wellas the second measuring port 73, are calibrated, it is possible tomeasure the group delay of the photodiode 72. Also other parameters ofthe photodiode 72 can be measured with this setup.

By way of further example, in order to perform such a measurement, themeasuring port 70 generates a radio frequency signal and sends is to theoptical interface 71. The optical interface 71 generates an opticalsignal therefrom and transmits it to the photodiode 72. This can occurusing an optical fiber or through an air gap. The photodiode 72generates a radio frequency response signal, which is then measured bythe measuring port 73.

FIG. 7 shows a sixth embodiment of a vector network analyzer adapted toperform S-parameter measurements on device(s) under test, in accordancewith example embodiments of the present invention. In FIG. 7 , themeasuring device 8 comprises a measuring port 80, which is comprised ofa signal generator 81, connected to a pulse generator 82, which in turnis connected to a coupler 83. The measuring device 8 further comprisesan optical interface 85, which is in practice a photodiode, which isconnected to a second measuring port 86.

By way of example, when performing a measurement, the signal generator81 generates a radio frequency signal which is provided to the pulsegenerator 82. The pulse generator 82 then generates accurately definedpulses of known spacing and timing, based on the radio frequency signal,which are provided to the coupler 83. The coupler diverts a part of thesignal for measurement purposes, and sends the remaining signal to thedevice under test 84 (e.g., an optical modulator, such as a laserdiode).

The optical modulator 84 receives the electrical pulse signal andgenerates an optical output signal based on the electrical pulse signal.The optical signal is provided to the optical interface 85 (e.g.,received by the photodiode), and converted to a radio frequency signal,which is provided to the second measuring port 86. The first measuringport 80, the second measuring port 86 and the optical interface 85 maythereby be calibrated with regard to each other, and thus it is possibleto measure the group delay of the optical modulator 84, as well asfurther parameters thereof.

FIG. 8 shows a first embodiment of a method for measuring the scatteringparameters of device(s) under test, in accordance with exampleembodiments of the present invention. In step 500, a device under testis connected to a digital interface of a vector network analyzer. Instep 501, the device under test is connected to a further measuring portof the vector network analyzer. In step 502, a first digital measuringsignal is supplied to the device under test by the first digitalinterface. In step 503, a second measuring signal, which is generated bythe device under test as a reaction to receiving the first digitalmeasuring signal, is measured at the further measuring port of thevector network analyzer. In step 504, S-parameters of the device undertest are determined from the first analog measuring signal and thesecond analog measuring signal.

FIG. 9 shows a second embodiment of a method for measuring thescattering parameters of device(s) under test, in accordance withexample embodiments of the present invention. In FIG. 9 , the reversemeasuring direction than in FIG. 8 is shown. In step 600, the deviceunder test is connected to a digital interface of a vector networkanalyzer. In step 601, the device under test is connected to a furthermeasuring port of the vector network analyzer. In step 602, a thirdanalog measuring signal is supplied to the device under test via thefurther port. In step 603, a fourth digital measuring signal is measuredat the digital interface, and a fourth analog measuring signal isdetermined therefrom. In step 604, the S-parameters of the device undertest are determined from a comparison of the third analog measuringsignal and the fourth analog measuring signal.

FIG. 10 shows a third embodiment of a method for measuring thescattering parameters of device(s) under test, in accordance withexample embodiments of the present invention. In FIG. 10 , a measurementof a device under test having two digital input ports, as shown in FIG.4 , is shown. In step 700, a device under test is connected to a firstdigital interface of the vector network analyzer. In step 701, thedevice under test is connected to a second digital interface of thevector network analyzer. In step 702, the device under test is connectedto a first further measuring port of the vector network analyzer. Instep 703, the device under test is connected to a second furthermeasuring port of the vector network analyzer. In step 704, a fifthmeasuring signal is provided to a first digital interface. In step 705,a sixth measuring signal is provided to a second digital interface ofthe vector network analyzer. In step 706, a seventh analog measuringsignal is provided to the first further measuring port of the vectornetwork analyzer. In step 707, an eighth analog measuring signal ismeasured at the second further measuring port of the vector networkanalyzer. In step 708, S-parameters of the device under test aredetermined from the fifth, sixth, seventh and eighth analog measuringsignals.

The embodiments of the present invention can be implemented by hardware,software, or any combination thereof. Various embodiments of the presentinvention may be implemented by one or more application specificintegrated circuits (ASICs), digital signal processors (DSPs), digitalsignal processing devices (DSPDs), programmable logic devices (PLDs),field programmable gate arrays (FPGAs), processors, controllers,microcontrollers, microprocessors, or the like.

Various embodiments of the present invention may also be implemented inthe form of software modules, processes, functions, or the like whichperform the features or operations described above. Software code can bestored in a memory unit so that it can be executed by a processor. Thememory unit may be located inside or outside the processor and cancommunicate date with the processor through a variety of known means.

The characteristics of the exemplary embodiments can be used in anycombination. Although the present invention and its advantages have beendescribed in detail, it should be understood, that various changes,substitutions and alterations can be made herein without departing fromthe spirit and scope of the invention as defined by the appended claims.

1. A measuring device, comprising: a first measuring port connected to aprocessor; an optical interface connected to the first measuring portvia a first coupler, wherein the optical interface is adapted to beconnected to an optical input or output of a device under test; a secondmeasuring port connected to the processor, and adapted to be connectedto a radio frequency input or output of the DUT; and wherein theprocessor is adapted to determine scattering parameters of the DUT basedon measuring signals transmitted to the DUT and received from the DUT bythe first measuring port and the second measuring port; and wherein theoptical interface is connected to the optical input of the DUT, and thesecond measuring port is connected to the RF output of the DUT, whereinthe first measuring port is adapted to generate a first analog measuringsignal and to provide the first analog measuring signal to the opticalinterface via the first coupler, wherein the optical interface isadapted to generate an optical measuring signal based on the firstanalog measuring signal, and to provide the optical measuring signal tothe optical input of the DUT, wherein the second measuring port isadapted to receive a second analog measuring signal generated by the DUTbased on the optical measuring signal and output by the RF output of theDUT, and wherein the processor is adapted to determine the S-parametersof the DUT based on the first analog measuring signal and the secondanalog measuring signal.
 2. The measuring device according to claim 1,wherein the measuring device is a vector network analyzer.
 3. Themeasuring device according to claim 1, further comprising: a firstmeasuring port connector adapted to connect the RF input or output ofthe DUT to the second measuring port; and an optical interface connectoradapted to connect the optical input or output of the DUT to the opticalinterface.
 4. The measuring device according to claim 3, wherein thefirst coupler is adapted to selectively connect the first measuring portto the optical interface or to a second measuring port connector.
 5. Themeasuring device according to claim 1, further comprising: a thirdmeasuring port connected to the second measuring port and to theprocessor; and a digital interface connected to the third measuring portvia a second coupler, wherein the digital interface is adapted to beconnected to a digital input or output of the DUT.
 6. The measuringdevice according to claim 5, wherein the second coupler is adapted toselectively connect the third measuring port to the digital interface orto a third measuring port connector.